Internal combustion engines for hybrid powertrain

ABSTRACT

The hybrid powertrain includes an internal combustion engine, a regenerative brake/motor and an electric energy storage device such as a battery. Preferably the internal combustion engine is a diesel engine with programmable injection events and programmable intake and exhaust valve events. The regenerative brake/motor is capable of operating as both an electric generator and as an electric motor. The battery receives electric energy from the regenerative brake. In additional to supplying electricity to the motor, the battery drives the engine accessories. The battery also supplies electric energy to keep the exhaust aftertreatment systems (Lean NOx, NOx absorber, PM Filter) at optimal temperature to improve conversion efficiency. A powertrain controller schedules the energy distribution and driving forces associated with both the diesel engine and the motor to maximize the vehicle fuel economy and to minimize the vehicle exhaust emissions.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/355,546, filed on Feb. 8, 2002.

FIELD OF THE INVENTION

[0002] The invention relates to internal combustion engines for use inhybrid powertrains to improve fuel economy and to reduce exhaustemissions.

BACKGROUND OF THE INVENTION

[0003] The recent development of hybrid powertrains in the automotiveindustry has demonstrated encouraging results for reductions in fuelconsumption and exhaust emissions. A vehicle with a hybrid powertrainusually includes an internal combustion engine, an electric generator,an electric motor, a battery and other equipment. In series hybridvehicles, the generator is driven by the mechanical output of theinternal combustion engine. The output of the generator is then combinedwith the output of the battery to drive the electric motor, such thatthe mechanical output of the motor drives the vehicle. In contrast, theparallel hybrid vehicle includes an internal combustion engine, aregenerative brake/motor and an electric energy storage device such as abattery and other equipment. PHVs are usually driven directly by themechanical output of the internal combustion engine. However, when thevehicle must be accelerated or decelerated at a rate that cannot beaccomplished by the internal combustion engine alone, or if the driveefficiency of the engine would be degraded if only the internalcombustion engine were used, the regenerative brake/motor, which ismechanically connected to the internal combustion engine, operates as anelectric motor (on acceleration) or as a regenerative brake (ondeceleration) to meet the required rate of acceleration or decelerationthrough the combined output of the internal combustion engine and theregenerative brake/motor.

[0004] The internal combustion engine of hybrid powertrain has narrowoperating range. In series hybrid vehicles, the internal combustionengine is not mechanical connected to the driving wheels. In parallelhybrid vehicles, the regenerative brake/motor provides rapidacceleration or deceleration. Therefore, the internal combustion engineused in hybrid powertrains can be optimized for better fuel economy andless exhaust emissions compared to conventional internal combustionengines.

[0005] Examples of hybrid vehicle and their operating modes have beendescribed in detail in several patents: For example, in U.S. Pat. No.5,656,921, a parallel hybrid vehicle is disclosed having power sourcesfrom a SI engine and an electric motor. It employs fuzzy logic rules toadjust the entries in the tables determining the power splitting betweenthe SI engine and the electric motor. The performance measure used toadjust the entries is given by the weighted ratio between the batterycurrent and fuel flow rate. In U.S. Pat. No. 5,943,918, granted to Reedand U.S. Pat. No. 6,164,400 granted to Jankovic, a hybrid powertrain isdescribed which uses power delivered by both the internal combustionengine and the electric motor. A shifting schedule was developed for amultiple ratio transmission to establishing a proportional relationshipbetween accelerator pedal movement and the torque desired at the wheel.U.S. Pat. No. 6,223,106 granted to Toru Yano et al. and U.S. Pat. No.6,318,487 granted to Yanase et al. each describe a hybrid vehiclecontrol system operable to prevent the battery from being overchargedduring regenerating braking. U.S. Pat. No. 5,725,064, describes acontrol system operable to open the intake and exhaust valves to reducethe pumping loss when the vehicle is operating in reverse or itselectric motor driving mode without using a clutch device to disconnectthe internal combustion engine from the transmission. Finally, U.S. Pat.No. 6,266,956 describes an exhaust emission control system for a hybridcar using a separate combustion device to heat the catalyst and toprovide hydrocarbons as the reducing agent to the lean NOx catalyst.

[0006] The primary focus of the above patents is the drivability of thehybrid vehicle. Unfortunately, little efforts have been applied to thedevelopment and integration of the internal combustion engines tooptimize the benefits of the hybrid powertrain for lower cost, betterfuel economy and lower exhaust emissions, especially, for the heavy-dutydiesel engines for the urban and on-highway truck and bus applications.

SUMMARY OF THE INVENTION

[0007] The present invention relates to advanced development of internalcombustion engines for hybrid powertrain applications and its exhaustemissions controls for urban and on-highway vehicles. The hybridpowertrain includes a diesel engine, a regenerative brake/motor and anelectric energy storage device such as a battery. The regenerativebrake/motor is capable of operating as both an electric generator as aresult of the regenerative braking to decelerate the vehicle and anelectric motor. The battery supplies electric energy to and receiveselectric energy from the regenerative brake/motor. A powertraincontroller schedules the driving forces supplied from at least one ofthe internal combustion engine and the electric motor.

[0008] The present invention also features a turbocharged diesel enginewith capabilities of multiple fuel injection events and rate shaping,variable valve timing, an exhaust aftertreatment system, engine braking,and battery powered accessories, such as water pump and cooling fan etc.

[0009] The electric motor is used to supply supplemental torque to thedrivetrain during acceleration and peak torque operating conditions andfurther acts as the sole power source during low load conditions. Theelectric motor will also serve as a regenerative brake during thevehicle decelerations. The regenerating brake, in combination with theengine exhaust brake or compression release brake, will providesufficient retarding power to maintain a proper vehicle speeds on a downslope road. The electricity generated by the regenerating brake will beused to charge the battery.

[0010] The powertrain controller schedules fuel delivery to the dieselengine, monitors the battery power, and schedules the battery powerdelivery to the electric motor. The diesel engine is calibrated so thatthe combined power of the drivetrain will deliver sufficient power tothe wheels and maintain drivability of the vehicle. Since the enginespeed can be measured, the desired engine torque is equal to the enginepower divided by engine speed Likewise, the desired motor torque isequal to the power desired from the electric motor divided by theelectric motor speed. The power at the wheels is approximately equal tothe sum of the power delivered from each of the power sources. Thedesired power at the wheels is the sum of the desired engine power andthe desired electric motor power.

[0011] This strategy requires a fuel-scheduling map for steady state andtransient operations of the diesel engine, as well as the functionalrelationship maps between the diesel engine and the electric motor. Thefuel injection system of the diesel engine has multiple injection eventcapability such as, for example, pilot injection, main injection, postinjection, and rate shaping capabilities, (i.e., triangle, boot, squareetc.). The fuel schedule map will specify the injection timing, rateshaping, injection pressure and quantity for best engine fuel economy,emission control, and drivability.

[0012] One aspect of the present invention is to power the engineaccessories with the battery of the hybrid powertrain. The accessoriesof current diesel engines are driven by the engines crankshaft whichreduces its power output and fuel economy. The present invention usesthe battery power, which is generated during the vehicle deceleration,to drive various engine accessories such as, for example, the coolingfan, water pump, engine control module, alternator, air compressor,power steering pump, and air conditioning compressor, etc.

[0013] Another aspect of the present invention is to apply the variablevalve timing capability of the diesel engine to reduce the pumping workduring the electric motor only mode, to perform cylinder cut-out, and tore-circulate EGR internally by delaying the exhaust valve closing and/orby early intake valve opening to reduce exhaust emissions (variableintake valve closing for increased compression ratio and/or Miller cycleoperation).

[0014] A further aspect of the invention is to use the battery power toheat the catalytic converter to increase the catalyst efficiency.Efficiency of the after treatment device such as, for example, an NOxabsorber and active lean NOx, are temperature dependent. The converterefficiency is decreased during partial load operation and at start up ofthe engine due to lower exhaust temperature. By externally heating thecatalyst through a battery-powered heater, the catalyst maintains at itsoptimal conversion efficiency to reduce exhaust emissions.

[0015] The fourth aspect of the invention is to open the exhaust valveduring the compression stroke to perform compression release braking incombination with the regenerative braking of the electric motor tocontrol vehicle speed and to prevent overcharge of the battery.

[0016] The fifth aspect of this invention to use motor assistedturbocharger during acceleration to improve the turbo chargerresponsiveness. The motor is powered the battery of the hybridpowertrain.

[0017] Further areas of applicability of the present invention willbecome apparent from the detailed description provided hereafter.However, it should be understood that the detailed descript and specificexamples, while indicating preferred embodiments of the presentinvention, are intended for purposes of illustration only since variouschanges and modifications within the fair scope of the present inventionwill become apparent to those skilled in this art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a schematic representation of a conventional hybridvehicle;

[0019]FIG. 2 is a schematic of a hybrid powertrain according to thepresent invention with integration of various engine and vehiclecomponents;

[0020]FIG. 3 is a schematic of an alternative hybrid powertrain equippedwith clutch and with integration of the engine and vehicle components;

[0021]FIG. 4 is a schematic of an internal combustion engine for use inhybrid powertrain applications;

[0022]FIG. 5 is an illustration of the catalyst conversion efficiency ofa hybrid powertrain;

[0023]FIG. 6 illustrates the capabilities of a diesel engine fuelinjection system;

[0024]FIG. 7 illustrates the valve lift of variable valve actuationsystem associated with the internal combustion engine of the presentinvention;

[0025]FIG. 8 is a schematic of the ECU.;

[0026]FIG. 9 is an operating diagram of steady state torque map for ahybrid vehicle;

[0027]FIG. 10 is an operating diagram of transient operating control ofa hybrid vehicle with motor assisted turbocharger;

[0028]FIG. 11 is a flow chart of a control strategy for a heavy-dutyhybrid vehicle;

[0029]FIG. 12A is a flow chart for the regenerative brake control; and

[0030]FIG. 12B is a flow chart for catalyst temperature and valve timingcontrol.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] A schematic of a conventional serial hybrid powertrain is shownin FIG. 1. The numeral 10 designates a turbocharged diesel engine foruse in a vehicle drivetrain. A motor/regenerative brake is shown at 20.Both diesel engine 10 and motor/regenerative brake 20 are connected to amultiple ratio transmission 30. Transmission 30 is mechanicallyconnected to a pair of vehicle driving wheels 40. A battery 50 serves asan energy storage device which is electrically connected tomotor/regenerative brake 20. An electronic controller unit 60 controlsthe overall drivetrain.

[0032] Referring to FIG. 2, the conventional drivetrain of FIG. 1 isshown to be modified to incorporate the features of the presentinvention. Specifically, FIG. 2 shows an integrated internal combustionengine 10A with the hybrid powertrain. Engine 10A is shown to includevarious controllable systems including a fuel injection system 11, athrottle system 12, an engine retrading mechanism 13, an aftertreatmentsystem 14, a turbocharger 15, an intake/exhaust valve actuation system16 for cylinder cutout and variable valve timing, in addition topower-operated accessories 17. Likewise, ECU 60A is shown to includeseveral control functions including a vehicle control function 61, anengine control function 62, a transmission control function 63, amotor-generator brake control function 64, and a battery controlfunction 65.

[0033]FIG. 3 shows an alternative configuration for the integratedinternal combustion engine 10A within the hybrid powertrain.Specifically, a clutch device 70 is placed in between internalcombustion 10A engine and motor 20.

[0034]FIG. 4 shows more details of the integration of the internalcombustion engine and the hybrid powertrain. The clean air passesthrough an air filter 100 to a compressor 102. Compressor 102, which isdriven by a turbine 105, increases the pressure of the air. Air iscooled when it passes through a charge air cooler 104 to increase theair density before entering the intake manifold 106.

[0035] The energy of the exhaust air is used to drive turbine 105 withvariable geometric nozzles 108. A high-speed motor 110, which is poweredby battery 50 of the hybrid powertrain, will be used to increaseturbine's responsiveness at part load operating condition and duringacceleration.

[0036] Harmful pollutants, such as NOx and particulate matters (PM), areremoved from the exhaust gas before the discharging to the ambient. Theefficiency of the after treatment system is temperature dependent. Theconversion efficiency is lowered due to low exhaust temperature duringlow speed and part load and start up operating conditions. An electricheater 112 is used to heat the after treatment system at its optimumconversion temperature at all engine-operating conditions. Battery 50 ofthe hybrid powertrain provides the power to electric heater 112. Theconversion efficiency comparison with and without electric heat is shownin FIG. 5.

[0037] The engine coolant is circulated to cool the engine by awater-pump 114. Hot coolant flows to a radiator 116, which is cooled bya fan 118. Instead of being driven by the engine crankshaft, water pump114 and cooling fan 118 are powered by battery 50 of the hybridpowertrain.

[0038] The capability of diesel engine fuel injection system 11 is shownin FIG. 6. It has the multiple injection and rate shaping capabilities.The pilot injection reduces the combustion noise and the NOx emissions.The first post injection reduces PM emissions with minimum fuel economypenalty. The second post injection provides hydrocarbon species forcatalytic converter to reduce NOx emissions.

[0039] Valve actuators associated with valve actuation mechanism 16provide variable timing capabilities and its valve lift profile is shownin FIG. 7. The Valve actuators change the opening and closing timing ofthe intake and exhaust valves, as well as to reopen the valves. Byreopening the intake and exhaust valves, it will reduce the pumping lossduring the motor only operating mode of the hybrid powertrain. Bypre-opening the intake valve during the exhaust blow down stroke, asmall portion of the exhaust gas discharges to the intake manifold. Thisportion of the exhaust gas will be readmitted to the cylinder to mixwith fresh air. It is called internal exhaust gas recirculation. Itreduces the NOx formation during diesel engine combustion process.Another EGR configuration is to reopen the exhaust valve during theintake stroke. The exhaust gases will reentry from the exhaust manifoldto the cylinder due to higher pressure of the exhaust manifold.

[0040] In combination of the diesel engine's injection capabilities andthe valve actuation capabilities, one or more cylinders can be cut outduring part load or the motor only operating modes to maximize the fueleconomy.

[0041]FIG. 8 shows the inputs and outputs of electronic controller 60A.The inputs to the electronic controller include the vehicle torquerequirements, vehicle speed, engine speed, engine boost pressure andtemperature, battery power level, transmission gear and motor torquelevel etc. The outputs include engine speed, torque, engine fueling map,motor torque, transmission gear and retarding power etc.

[0042]FIG. 9 shows a steady state map with the engine torque output 130from the diesel engine 10A and the motor torque output 120 from electricmotor 20. The hybrid powertrain demonstrate that vehicle emissions canbe effective reduced. For example, if the hybrid powertrain outputs 500HP at 1200 engine rpm (in which the diesel engine outputs 300 HP at NOxemission level of 3.5 g/hp-hr and the electric motor outputs 200 hp) thehybrid powertrain emission will be equivalent to a 500 HP engine withNOx emission level of 2.1 g/hp-hr.

[0043]FIG. 10 shows time sequences for the hybrid powertrain's istransient responses. Step 150 shows a torque command of a vehicle. Acommand increases torque demand at time t₁ and decreases at time t₅. Themotor output torque 160 reaches its maximum value at time t₂. The engineoutput torque 170 reaches a specific value at time t₄. The combinedtorque of the hybrid powertrain 180 reaches a specified value at timet₃, which has shorter response time than the internal combustion enginealone. As seen, the hybrid powertrain also has fast response at thedecrease of command torque.

[0044]FIG. 11 is a flowchart showing the control strategy of the hybridpowertrain. The powertrain ECU 60A in FIG. 3 read the vehicle torquerequirement and the engine operating parameters, such as speed, fuelinjection rate, boost pressure and temperature etc. in step 210. The ECU60A calculates the engine torque output in step 220. Step 230 comparesthe vehicle operating torque T_(veh) and the vehicle torque requirementT_(req). If T_(req) is less than T_(veh), then step 280 indicates thatvehicle braking is required to reduce the powertrain torque output, andthe motor brake regeneration is activated as indicated at step 270. Ifthe required torque T_(req) is larger than T_(veh), then step 240indicates that the engine torque output is checked. If the engine torqueT_(eng) is less than T_(req), the hybrid powertrain will switch to themotor/engine dual operating mode at step 250. Otherwise, the hybridpowertrain will operate in the engine only mode at step 260.

[0045] The powertrain regenerating brake control flowchart is shown inFIG. 12A. The ECU 60A reads a deceleration command input at step 310,and calculates the deceleration torque requirement (based on vehiclespeed and other operating parameters, engine brake torque, and the motorbrake torque) at step 320. If the required deceleration torque isgreater than the motor regenerative brake torque, which is determined atstep 330, then engine braking will be activated in combination with themotor regenerating brake, as shown at step 340. Otherwise, the vehiclewill operate in the motor regenerating brake only mode at step 370.During the engine braking mode, the engine brake noise will be checkedin order to comply with local noise regulations, as indicated by step350. If the braking noise level is not acceptable, the engine valvetiming can be varied to reduce the brake noise as shown in step 360.

[0046]FIG. 12B shows a control strategy related to catalyst temperaturefor reducing engine exhaust emissions. At step 400, the operatingparameters of the diesel engine are read. Thereafter, step 430 comparesthe exhaust gas temperature with the temperature required for effectivecatalyst operation. If the exhaust gas temperature is lower than therequired temperature, the exhaust valve timing will be adjusted throughvariable valve actuation (VVA) device to increase the temperature, asindicated in step 410. Step 440 determines the hydrocarbon concentrationof the exhaust gas since a proper hydrocarbon concentration is requiredfor effective NOx adsorption and lean NOx catalyst operations. If thehydrocarbon concentration is lower than specified, post injection orauxiliary exhaust manifold injection is required to add hydrocarbonsinto the exhaust gas stream in step 420. The catalyst temperature isdetermined in step 450 for optimum emissions reduction performance. Ifthe catalyst temperature is lower than the optimum performancetemperature, a battery powered catalyst heater will be turned on toincrease the catalyst temperature in step 460.

[0047] Although a particular control strategy is disclosed, it will beapparent to persons skilled in the art that modifications may be madewithout departing from the scope of the invention. All suchmodifications as well as equivalents thereof are to be included withinthe scope of the following claims.

What is claimed is:
 1. A hybrid powertrain for urban and on-highwayvehicle comprising a diesel engine, an electronic controller, atransmission, an electric motor/regenerative brake, and a battery; saidtransmission having torque input from said diesel engine and saidelectric motor; said diesel engine having a turbo charger and a fuelscheduling means for regulating fuel delivery in response to the vehicledemand for speed and torque; said electrical motor can function asregenerating brake to retarding the vehicle during deceleration of thevehicle; said electric motor can function as generator to charge thebatter during the regenerative brake process; said electronic controllerhaving stored the fueling map as a function engine operating parameters,such as boost pressure, temperature, engine speed, etc. for steady stateand transient operations of meeting the government emissionsregulations; said electronic controller having stored the relationshipof the electric motor speed and electric motor current; the relationshipof the battery power and the current output; the relationship of batterycharging current and the regenerative retarding power; said controllerhaving stored the relationship between the output torque of dieselengine and the output torque of the electric motor for providingcombined torque output to meet the vehicle torque requirement
 2. Thehybrid powertrain as set forth in claim 1 includes the torque input fromboth the said diesel engine and the said electric motor for steady statecalibration;
 3. The hybrid powertrain as set forth in claim 1 includesthe torque input from both the said diesel engine and the said electricmotor for transient state calibration;
 4. The hybrid powertrain as setforth in claim 1 wherein said electric controller including means forscheduling the torque delivery for the diesel engine and the motor tomeet the total torque demand.
 5. The hybrid powertrain as set forth inclaim 1 said electronic controller could sense the battery power level.6. The said battery in claim 1 will be charged during regeneratingbraking and delivery power to the motor to provide torque to thedrivetrain.
 7. The hybrid powertrain as set forth in claim 1 saidelectronic controller could schedule power delivery by the diesel engineand the motor if the battery power level is too low.
 8. A hybridpowertrain for urban and on-highway vehicle comprising a diesel engine,an electronic controller, a transmission, an electric motor/regeneratingbrake, and a battery; said transmission having torque input from saiddiesel engine and said electric motor/regenerating brake. A internalcombustion engine used in a hybrid powertrain consists of enginecompression release device and/or engine exhaust brake,
 9. Said dieselengine have auxiliary brake system such as exhaust engine brake, thecompression release engine brake in addition to the regenerating brake.10. The hybrid powertrain as set forth in claim 7, said electric motorcan function as regenerating brake to retarding the vehicle duringdeceleration of the vehicle.
 11. The hybrid powertrain as set forth inclaim 7 said electric motor can function as generator to charge thebatter during the regenerating brake process.
 12. The hybrid powertrainas set forth in claim 7 said electronic controller could estimate theretarding torque requirement to maintain proper vehicle speed.
 13. Thehybrid powertrain as set forth in claim 7 said electronic controllercould schedule the retarding torque delivery by the engine brake if theretarding torque required by the vehicle is larger than the torqueavailable by the regeneration braking.
 14. The hybrid powertrain as setforth in claim 7 said electronic controller could sense the batterypower to avoid over charging and the effectiveness of the regeneratingbrake.
 15. A hybrid powertrain for urban and on-highway vehiclecomprising a diesel engine, an electronic controller, a transmission, anelectric motor/regenerating brake, and a battery; said transmissionhaving torque input from said diesel engine and said electricmotor/regenerating brake. A internal combustion engine used in a hybridpowertrain consists of: a. A engine have at least one cylinder with atleast one intake and one exhaust valve; b. A fuel injection system,which is able to deliver fuel in multiple injection events per cycle andin different rate shaping. c. A motor assisted turbocharger system. d.An exhaust aftertreatment device with battery powered electric heater.e. A variable valve timing device which is capable of controlling thevalve opening events and timing; f. Battery powered accessory devicesuch as cooling fun, water pump, engine control module etc. g. Enginecompression release device and/or engine exhaust brake
 16. The hybridpowertrain as set forth in claim 1 wherein said diesel engine ischaracterized by with NOx and PM exhaust emissions for each engine speedvalue and torque value.
 17. Said diesel engine has its accessories, suchas water pump, cooling fan etc is powered by the battery of the hybridpowertrain.
 18. Said diesel engine has variable valve timing capabilityto hold both intake and exhaust valve open to reduce the pumping losswhen the hybrid powertrain is at motor only operation mode.
 19. Saiddiesel engine has cylinder cut-out capability to reduce fuel consumptionwhen the hybrid powertrain is at engine only or at engine and motorcombined operating mode.
 20. Said diesel engine has variable valvetiming capability to open the intake valve during blow down stroke ordelay the intake valve closing to induce exhaust gas re-circulationinternally for NOx emissions reduction.
 21. Said diesel engine will haveexhaust aftertreatment systems (Lean NOx, NOx absorber, PM Filter) toreduce exhaust emissions. The heater power by the said battery is usedto maintain the aftertreatment temperature to achieve optimum conversionefficiency.
 22. Said diesel engine will have multiple injectioncapabilities to control the exhaust species for optimum catalystconversion efficiency.
 23. The said diesel engine will have variabletiming capability to control the exhaust temperature to allow thecatalyst at its optimum conversion level.
 24. The said diesel enginewill have variable timing capability to control the braking noise whenthe engine compression release brake is used.
 25. The said diesel enginewill have variable timing capability to reduce warm up period for coldwhether operations.